Too loud signals are dampened by the brain's prepulse inhibition system.
When the brain is tranquilized however (by drugs, medicine, hypoglycemia or extreme tiredness) it will deactivate this system.
After this it is possible the brain gets awake before the prepulse inhibition system gets active again, causing schizophrenia.
New research by Karen Alsene discovered the prepulse inhibition system can be prohibited to deactivate itself by using a lipid-soluble beta blocker (propranolol/metoprolol two times a day).
http://www.nature.com/npp/journal/v35/n12/full/npp2010106a.html
